1. The Field of the Invention
The present invention relates generally to systems, methods, and devices for high speed data transmission. More particularly, embodiments of the invention concern systems, methods, and devices for providing a redundant and robust status link in a multi-channel optical communication system and applications thereof.
2. The Relevant Technology
Computing and networking technology have transformed our world. As the amount of information communicated over networks has increased, high speed transmission has become ever more critical. Many high speed data transmission networks rely on optoelectronic devices for facilitating transmission and reception of digital data embodied in the form of optical signals over optical fibers. Optical networks are thus found in a wide variety of high speed applications ranging from modest Local Area Networks (LANs) to backbones that define a large portion of the infrastructure of the Internet.
Typically, data communication in such networks is implemented by way of an optoelectronic device, such as a transceiver or transponder, that includes an optical transmitter for optical data transmission and an optical receiver for optical data reception. As demands for higher data transmission speeds between points in optical networks have increased, optoelectronic devices have been developed with multiple optical transmitters and multiple optical receivers to transmit and receive optical signals over multiple signal channels. These multi-channel optoelectronic devices often utilize one of several different types of signal channels, such as multiple ribbon fibers, multiple wavelengths or in-phase and quadrature-phase channels. Every signal channel requires its own transmitter and receiver. To support N duplex channels, a multi-channel optoelectronic device therefore requires at least N transmitters and at least N receivers.
It is often desirable in optical networks to implement a status link between optoelectronic devices, whether the devices are multi-channel or single-channel. The status link can be used to provide information to the devices about each device and/or the physical link between the devices. Conventional status links are often implemented by signaling between optoelectronic devices over spare fibers and/or by superimposing the status link out-of-band (OOB) on a single signal channel. These schemes require additional components and/or are subject to the same failure modes as the signal channel.
Additionally, one of the problems associated with multi-channel optical links is that of eye safety. Consider a multi-channel optical link that includes a first multi-channel optoelectronic device at one location and a second multi-channel optoelectronic device at another location. One or more first fibers couple the transmitters of the first device to the receivers of the second device while one or more second fibers couple the transmitters of the second device to the receivers of the first device. If either of the first or second fibers is removed from the first or second device, one or more transmitters may still be transmitting, either over a fiber(s) or into free-space, exposing emitted optical signals to view. At certain frequencies, the exposed optical signals can cause minimal to severe damage to a human eye if viewed. The potential damage may increase as the number of transmitters emitting optical signals increases, thereby posing an eye safety risk even if each individual transmitter's power is well below what is considered safe.
Conventional solutions for ensuring eye safety limit the optical link budget or implement mechanical interlocks or shutters in the optical fibers. In the case of the former, the limited optical link budget limits the distance over which information can be transmitted and/or the maximum number of transmitters that can be implemented before the aggregate power of the link exceeds the nominal eye safety limit. In the case of the latter, the mechanical interlocks/shutters are ineffective if an opening occurs at a point other than at the interlock or shutter trigger points. Additionally, both conventional solutions may require the use of additional components in the optical link, increasing its cost and/or complexity.
Additionally, multi-channel optical links are typically required to meet one or more specifications over the lifetime of the hardware. Age and other factors can degrade the performance of certain components, degrading in turn the quality of the optical signals transmitted over the optical links. For example, the optical signals emitted by a transmitter often attenuate as the transmitter ages, even though the transmitter bias current remains constant. This degradation in signal strength can increase bit error rates and ultimately result in loss of the signal. For this reason, optoelectronic devices and other hardware must be designed to operate at the worst operating point at the end of life for the hardware, which may produce operating inefficiencies at the beginning of life of the hardware.
In some cases, degradations in optical signal quality may be compensated for by adjusting one or more parameters. For instance, increasing the transmit power of an aging transmitter can compensate for age-attenuation. Some optoelectronic devices implement digital monitor and control techniques with a controller to identify degradation effects and compensate accordingly. However, not all degradation effects can be identified, in which case some may remain untreated. For example, an optoelectronic device may be unable to identify degradation effects outside of the device which nonetheless affect optical signal quality, such as the degradation of the optical medium over which a transmitter emits an optical signal or degradation of the mechanical connection between the device and the optical medium. Because the device is unable to identify the problem, the device does nothing to compensate for it.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.